Species-specific variation in germination rates contributes to spatial coexistence more than adult plant water use in four closely-related annual flowering plants

1. Spatial partitioning is a classic hypothesis to explain plant species coexistence, but evidence linking local environmental variation to spatial sorting, demography, and species’ traits is sparse. If co-occurring species’ performance is optimized differently along environmental gradients because of trait variation, then spatial variation might facilitate coexistence.
2. We used a system of four naturally co-occurring species of Clarkia (Onagraceae) to ask if distribution patchiness corresponds to variation in two environmental variables that contribute to hydrological variation. We then reciprocally sowed Clarkia into each patch type and measured demographic rates in the absence of congeneric competition. Species sorted in patches along one or both gradients, and in three of the four species, germination rate in the “home” patch was higher than all other patches.
3. Spatially variable germination resulted in the same three species exhibiting the highest population growth rates in the...

1. 空间分区（Spatial partitioning）是阐释植物物种共存的经典假说，但将局地环境变异与空间分选（spatial sorting）、种群统计学（demography）及物种性状建立关联的证据仍较为匮乏。若共存物种的适合度因性状差异沿环境梯度呈现差异化优化模式，则空间变异或可促进物种共存。
2. 我们以4种自然共存的克拉克花属（Clarkia，Onagraceae）物种为研究系统，探究物种分布的斑块格局是否与两类驱动水文变异的环境因子的变异相匹配。随后我们将各克拉克花属物种交叉播种于不同斑块生境，并在排除同属竞争的条件下测定其种群统计学参数。结果显示，物种沿其中一条或两条环境梯度在斑块中发生空间分选；4个物种中有3个在其“原生”斑块中的萌发率显著高于其余所有斑块。
3. 空间异质性引发的萌发差异，使得上述3个物种在对应的原生斑块中展现出最高的种群增长率……